extracted base Resolver class from SyckResolver (going to move ahead w/ PsychResolver now)
refactoring towards more unified implementation between Syck and Psych (prep work for whitelisting)
fixed PsychResolver for older versions of Psych (Ruby 1.9.2)
simplified (?) Psych implementation slightly, to bring more in line w/ Syck one
switched up specs to test PsychResolver rather than PsychHandler
got a tag whitelist implementation working w/ Psych - see #21
whew, OK... whitelisted tags implementation is working in both Syck and Psych; but it's MESSY (will clean up tomorrow!) - see #21